Enclosure for electric device, in particular for surge arrester, including a molded, electrically insulating envelope

Abstract

An enclosure for electric device, in particular for surge arrester, comprises an outer, cylindrical envelope and an inner wall both made of electrically non conducting materials. One of the ends of the envelope is closed while the other is open. An electrode with a principal portion inside the enclosure extends through the envelope and projects outside the latter. Bolt anchors are used for fixing the enclosure on a mechanical support and for mounting a closure device on the open end of the envelope. The material constituting the inner wall is impervious to humidity and protects the envelope against breaking thereof by thermal shock caused for example by the production of an electric arc within the enclosure, while the material constituting the cylindrical envelope is a synthetic insulating material capable of withstanding a high mechanical tension. The envelope is molded on the inner wall and around the electrode and the bolt anchors, whereby the inner wall and the electrode are integrated to the envelope, and the bolt anchors are fixedly attached to the synthetic insulating material.

What is claimed is: 
     
       1. An enclosure for surge arresters, comprising: an outer envelope;   a hollow self supporting inner wall made of an electrically non conducting material impervious to humidity and protecting said outer envelop against breaking thereof by thermal shock caused by heat produced within the enclosure; and   anchor means for fixing the enclosure on a mechanical support;   said envelope being made of an insulating material having high mechanical tensile strength;   said envelope being molded on said inner wall so that said inner wall is integrated to said envelope;   said envelope being molded around said anchor means so that said anchor means are embedded within said outer envelope and thereby fixedly attached to said insulating material.   
     
     
       2. An enclosure according to claim 1, wherein said outer envelope is cylindrical. 
     
     
       3. An enclosure according to claim 2, wherein said cylindrical envelope comprises an inner surface which is frusto-conical. 
     
     
       4. An enclosure according to claim 1, wherein said anchor means comprise a plurality of bolt anchors. 
     
     
       5. An enclosure according to claim 1 further comprising an opening and additional anchor means for mounting on the enclosure a device for closing said opening, said insulating material being molded around said additional anchor means so that said additional anchor means are embedded within the insulating material constituting the outer envelope. 
     
     
       6. An enclosure according to claim 5, wherein said additional anchor means comprise a plurality of bolt anchors. 
     
     
       7. An enclosure according to claim 1, further comprising an electrode having a principal portion inside the enclosure, and an extension attached to said inside, principal portion, traversing said outer envelope, and projecting outside the enclosure, said outer envelope being molded around the electrode whereby said electrode is integrated to the outer envelope. 
     
     
       8. An enclosure according to claim 1, wherein the material constituting the outer envelope comprises a synthetic insulating material. 
     
     
       9. An enclosure according to claim 8, in which said synthetic insulating material comprises epoxy-concrete. 
     
     
       10. An enclosure according to claim 8, wherein said synthetic insulating material comprises polymeric concrete. 
     
     
       11. A cylindrical enclosure for surge arrester, comprising: an outer, cylindrical envelope having a first, closed end and a second, open end;   an inner wall made of an electrically non-conducting material impervious to humidity and protecting said cylindrical envelope against breaking thereof by thermal shock caused by the production of an electric arc within the enclosure;   an electrode located at the closed end of the cylindrical envelope and comprising a principal portion inside said enclosure and an extension attached to said inside, principal portion, traversing the outer envelope, and projecting outside the enclosure;   first anchor means mounted on the closed end of the outer envelope for fixing the enclosure to a mechanical support; and   second anchor means mounted on the open end of the cylindrical envelope for fixing a closure device of the said enclosure;   said envelope being made of an insulating material capable of withstanding a high mechanical tension, and being molded on the inner wall and around the electrode and the first and second anchor means, whereby said inner wall and said electrode are integrated to the cylindrical envelope, and the first and second anchor means are fixedly attached to the insulating material consituting the outer envelope.   
     
     
       12. A cylindrical enclosure according to claim 11, wherein the first and second anchor means comprise bolt anchors. 
     
     
       13. A cylindrical enclosure according to claim 11, wherein the closed end of the cylindrical envelope comprises an external cavity and at least one annular, external flange surrounding said envelope for adequately and electrically insulating said electrode from said mechanical support, the cylindrical envelope having a geometrical axis and said annular flange being located in a plane perpendicular to said geometrical axis. 
     
     
       14. A cylindrical enclosure according to claim 11, wherein said envelope has a geometrical axis and comprises a plurality of external, annular flanges each located in a plane perpendicular to said geometrical axis. 
     
     
       15. A cylindrical enclosure according to claim 11, wherein the cylindrical envelope defines a frusto-conical inner surface having a diameter which increases from the closed end towards the open end of the envelope, said inner wall being also frusto-conical. 
     
     
       16. A cylindrical enclosure according to claim 11, wherein the electrically non conducting material constituting said inner wall comprises frosted glass. 
     
     
       17. A cylindrical enclosure according to claim 11, wherein the insulating material constituting the outer envelope comprises a synthetic insulating material. 
     
     
       18. A cylindrical enclosure according to claim 17, wherein said synthetic insulating material comprises epoxy-concrete. 
     
     
       19. A cylindrical enclosure according to claim 17, wherein said synthetic insulating material comprises polymeric concrete. 
     
     
       20. A cylindrical enclosure according to claim 11, wherein the extension of said electrode radially traverses the cylindrical envelope. 
     
     
       21. A cylindrical enclosure according to claim 11, wherein said closure device of the enclosure comprises pressure limiting means. 
     
     
       22. A method of protecting electrical devices from damage due to voltage surges, comprising: molding an outer envelope around a hollow inner wall and an anchor means thereby forming an enclosure; said hollow inner wall being formed of an electrically non-conducting material impervious to humidity and protecting said outer envelope against breaking thereof by thermal shock caused by heat produced within the enclosure; said outer envelope comprising an insulating material having high mechanical tensile strength;   locating surge arrester components in said enclosure;   fixing said anchor means to a mechanical support;   connecting said enclosure in parallel with an electrical device to be protected having a pair of terminals;   whereby a closed circuit is created in said enclosure parallel to said electrical device to be protected when an over-voltage appears between the terminals of said electrical device.   
     
     
       23. The method according to claim 22 further comprising forming said outer envelope into a cylindrical shape. 
     
     
       24. The method according to claim 33 further comprising defining a frusto-conical inner surface of said cylindrical envelope. 
     
     
       25. The method according to claim 22 further comprising: forming an opening in said enclosure;   embedding an additional anchor means within said outer envelope;   mounting a closure device for closing said opening on said additional anchor means.   
     
     
       26. The method according to claim 25 further comprising integrating an electrode to said outer envelope; said electrode having a principal portion inside the enclosure, and an extension attached to said inside principal portion, traversing said outer envelope, and projecting outside the enclosure. 
     
     
       27. The method according to claim 22, including forming the outer envelope with a synthetic insulating material. 
     
     
       28. The method according to claim 27, including forming said synthetic insulating material with epoxy-concrete. 
     
     
       29. The method according to claim 27, including forming said synthetic insulating material with polymeric concrete. 
     
     
       30. A method of protecting electrical devices from damage due to voltage surges, comprising: molding an outer cylindrical envelope having a first, closed end and a second, open end around an inner wall and a first anchor means thereby forming an enclosure; said inner wall comprising an electrically non-conducting material impervious to humidity and protecting said outer envelope against breaking thereof by thermal shock caused by heat produced within the enclosure; said outer envelope comprising an insulating material having a high mechanical tensile strength;   locating surge arrester components in said enclosure;   integrating an electrode to the closed end of the cylindrical envelope, said electrode having a principal portion inside the enclosure, and an extension attached to said inside, principal portion, traversing the outer envelope, and projecting outside the enclosure;   fixing said anchor means to a mechanical support;   embedding a second anchor means in said insulating material at the open end of said cylindrical envelope;   mounting a closure device on said second anchor means;   connecting said enclosure in parallel with an electrical device to be protected having a pair of terminals;   whereby a closed circuit is created in said enclosure parallel to said electrical device to be protected when an over voltage appears between the terminals of said electrical device.   
     
     
       31. The method according to claim 30 further comprising forming a plurality of external, annular flanges on said cylindrical envelope, said flanges each being located in a plane perpendicular to a geometrical axis of said cylindrical envelope. 
     
     
       32. The method according to claim 30 further comprising defining a frusto-conical inner surface of said cylindrical envelope, said surface having a diameter which increases from the closed end towards the open end of the envelope. 
     
     
       33. The method according to claim 30 including forming said electrically nonconducting material constituting said inner wall with frosted glass. 
     
     
       34. The method according to claim 30 including forming the material constituting the outer envelope with a synthetic insulating material. 
     
     
       35. The method according to claim 34 including forming said synthetic insulating material with epoxy-concrete. 
     
     
       36. The method according to claim 34 including forming said synthetic insulating material with polymeric concrete.